The aim of the present study was to develop a relationship to evaluate grip force using the electromyogram (EMG) in isometric anisotonic conditions. The EMGs of the flexor digitorum superficialis (FDS) and the extensor digitorum (ED) were recorded in 3 flexion-extension positions of the wrist (30 degrees flexion, 30 degrees extension, and 60 degrees extension) associated with 3 positions of the forearm (70 degrees pronation, prono-supination, and 70 degrees supination). For each position, the participants had to follow linear ramp targets (2 rates of increase and decrease) displayed on an oscilloscope. The results show the best fit is a quadratic type force-EMG relationship. Some aspects such as the rate of force variation and the forearm and wrist positions are then discussed along with the limitations of the relationship.